For me, roll casting is a necessary evil for some of the streams I fish. I use just about any rod in my quiver, from a nice slow cane rod to very fast graphite. My longest casts and best results are with a double taper line. One of my favorite rods for roll casting and overhead casting a multiple fly rig is my new Global Dorber 10 foot 4 wgt. Very nice rod.
When comparing spey casts to roll casts you have to remember that a spey cast is primarily a change of direction cast that aerializes the majority of the line. The spey lines are considerably heavier than a normal line and have very long bellies allowing the line weight plus the leader anchor to load the rod. Behind the belly of the spey line is a much smaller running line. On short belly spey lines the belly can measure over 45 feet. That's half the length of a normal fly line. At least that much line is usually out of the guides when casting.
You can use spey casts with a single hand rod, even add in a haul for more line speed.
For my use, a medium fast rod with a double taper line seem to do the business. Your mileage may vary.
REE